1. Field of the Invention
The present invention relates to a method and an apparatus for informing an active subscriber of the disconnection of a held subscriber in a call-waiting service.
2. Description of the Related Art
A call-waiting service is widely utilized as one of the services provided by a central office exchange. In the call-waiting service, when a subscriber A talking with a subscriber B is called by another subscriber C, a call-waiting tone (CWT) is sent to the talking subscriber A if the subscriber A is provided with the call waiting service, to thus inform the subscriber A of a call by another subscriber. If the subscriber A presses the switchhook (hooking) of a telephone set, the subscriber A is connected to the calling subscriber C and the subscriber B is held. In this situation, if the subscriber A presses the switchhook (hooking), the subscriber A is again connected to the subscriber B and the subscriber C is held.
The above conventional call-waiting service has the following shortcomings. Normally, the held subscriber B maintains an off-hook state until the held subscriber B is released. However, if the held subscriber B wishes to terminate a conversation with the subscriber A and hooks the handset on the telephone set, the subscriber A does not notice that the subscriber B has been disconnected until the subscriber A attempts to talk with the subscriber B who has been disconnected and therefore the subscriber A hears a busy tone (BT). Thus, the subscriber A is obliged to press the switchhook and hear the BT even when the held subscriber B is disconnected.